Phenotypes associated with this allele

• Allele Symbol: Lbx1^tm1Gld
• Allele Name: targeted mutation 1, Martyn Goulding
• Allele ID: MGI:2182635
• Summary: 3 genotypes

Jump to	Allelic Composition	Genetic Background	Genotype ID
hm1	Lbx1^tm1Gld/Lbx1^tm1Gld	involves: 129S1/Sv	MGI:3773046
hm2	Lbx1^tm1Gld/Lbx1^tm1Gld	involves: 129S1/Sv * C57BL/6	MGI:3773045
cx3	Lbx1^tm1Gld/Lbx1^tm1Gld Tlx3^tm1Sjk/Tlx3^tm1Sjk	involves: 129S1/Sv * 129X1/SvJ	MGI:3773047

Genotype
MGI:3773046

hm1

• Allelic Composition: Lbx1^tm1Gld/Lbx1^tm1Gld
• Genetic Background: involves: 129S1/Sv

• ♀: phenotype observed in females
• ♂: phenotype observed in males
• N: normal phenotype

nervous system

abnormal GABAergic neuron morphology ( J:102513 )

• at ages E11.5 and E12.5, neurons expressing GABAergic markers are reduced in dorsal spinal cord; number of neurons expressing Gad1 is lower than in wild-type mice in lumbar spinal cord at E12.5

abnormal glutaminergic neuron morphology ( J:102513 )

• at E12.5, a marked increase in dorsal glutaminergic neurons (VGLUT2-positive) neurons is seen in the caudal spinal cord relative to controls; this increase corresponds to decrease in GABAergic neurons, suggesting switch of neurotransmitter fate

muscle

muscle phenotype ( J:98439 )

N • perineal muscles form normally

abnormal skeletal muscle morphology ( J:98439 )

• all distal limb muscles are absent

Genotype
MGI:3773045

hm2

• Allelic Composition: Lbx1^tm1Gld/Lbx1^tm1Gld
• Genetic Background: involves: 129S1/Sv * C57BL/6

mortality/aging

perinatal lethality, complete penetrance ( J:56498 )

• majority of mutants are born dead; a living mutant was born and died within 2 hours

muscle

muscle phenotype ( J:56498 )

N • deep muscles of back, intercostals muscles and ventral body wall muscles are comparable to wild-type and heterozygous littermates

N • tongue muscles and diaphragm muscle form in homozygotes

N • small differences are observed in distribution of muscle tissue within the diaphragm, but no significant difference is seen in overall organization of diaphragm; tongue muscle shows no significant difference in size or organization relative to wild-type newborns

abnormal muscle precursor cell migration ( J:56498 )

• at E9.5, muscle precursors (Pax 3-positive cells) are clustered in the trunk, beneath the ventrolateral lip of dermomyotome; at E10.5, no Pax 3-positive cells are observed in forelimbs, while an enlarged stream of cells is seen adjacent to ventral aspect of limb at posterior forelimb levels

• in hindlimbs at E10.5, precursors delaminate but do not migrate very far from ventral edge of dermomyotome

abnormal limb muscle morphology ( J:56498 )

• proximal forelimb flexors (those connecting humerus, radius, and ulna to carpal bones) are present, but truncated along proximodistal axis of limb; muscle tissue is present only at proximal end of bones, giving way to tendon midway between wrist and elbow, while at P0, skeletal muscle extends 75% of distance from elbow to wrist

abnormal myogenesis ( J:56498 )

• MyoD-positive cells are absent from hindlimbs in E13.5 embryos, with exception of anlage of gluteus medius and another unidentified muscle

• extensor muscle anlagen in forelimbs are absent at E13.5, while flexor muscles show substantial size reduction midway between wrist and elbow

absent hypaxial muscle ( J:56498 )

• all hindlimb muscles are absent, except for gluteus medius and one other unidentified hypaxial muscle in newborn mice

• all only 2 hindlimb suspension muscles (quadriceps lumborum, pubococcygeus) are retained in homozygotes, suggesting hypaxial derivation of other suspension muscles

• in forelimbs, all extensor muscles are absent, but some flexor muscles are present

• muscles on extensor side of scapula (muscles derived from dorsal muscle mass) are absent, but muscle on flexor side is present but reduced in size

decreased skeletal muscle mass ( J:56498 )

• newborn mice display severe reduction in muscle mass in shoulders, pelvic girdle and limb extremities

limbs/digits/tail

abnormal forelimb morphology ( J:56498 )

• forelimbs are hyperflexed and thinner than in wild-type neonates

abnormal hindlimb morphology ( J:56498 )

• severely reduced in girth in newborn mice

abnormal limb muscle morphology ( J:56498 )

• proximal forelimb flexors (those connecting humerus, radius, and ulna to carpal bones) are present, but truncated along proximodistal axis of limb; muscle tissue is present only at proximal end of bones, giving way to tendon midway between wrist and elbow, while at P0, skeletal muscle extends 75% of distance from elbow to wrist

cellular

abnormal muscle precursor cell migration ( J:56498 )

• at E9.5, muscle precursors (Pax 3-positive cells) are clustered in the trunk, beneath the ventrolateral lip of dermomyotome; at E10.5, no Pax 3-positive cells are observed in forelimbs, while an enlarged stream of cells is seen adjacent to ventral aspect of limb at posterior forelimb levels

• in hindlimbs at E10.5, precursors delaminate but do not migrate very far from ventral edge of dermomyotome

Genotype
MGI:3773047

cx3

• Allelic Composition: Lbx1^tm1Gld/Lbx1^tm1Gld; Tlx3^tm1Sjk/Tlx3^tm1Sjk
• Genetic Background: involves: 129S1/Sv * 129X1/SvJ

nervous system

nervous system phenotype ( J:102513 )

N • at hindlimb level, reduction in glutaminergic neurons observed in Lbx1 mutants is reversed

abnormal GABAergic neuron morphology ( J:102513 )

• at age E12.5, neurons expressing GABAergic markers are reduced in dorsal spinal cord; similar to phenotype observed in Lbx1-single mutants